1. Field of the Invention
This invention relates to an apparatus for a hydrator in a system for transferring a dry chemical from a source and hydrating the chemical, particularly soda ash, which automatically and periodically flushes the hydrator with water to remove any solids accumulation which may occur during hydration, without the need to shut down the system.
2. Description of the Related Art
Various means have been described for transferring and hydrating dry chemicals. U.S. Pat. No. 3,512,842 relates to a method for unloading rail cars in which a slurry is formed inside the rail car and then is pumped out. Such a process has numerous drawbacks, however, including the risk of overflowing or foaming within the car; the need for specialized rail cars adapted for use in the slurrying process; the possibility of corrosive solutions being formed and damaging the rail car; and problems with the residual moisture causing caking and the formation of hard, slowly dissolving lumps when liquid is added to the large quantity of solid. A similar approach is described in U.S. Pat. No. 4,189,262.
Commonly assigned U.S. Pat. No. 4,884,925, incorporated by reference herein, relates to an apparatus and method for transfer and slurrying of hydratable dry bulk chemicals. The apparatus has a sealed solvation hopper positioned between a liquid driven eductor and a fitting for connection to a storage container such as a railroad car. At the inlet end of the solvation hopper is a chemical inlet pipe which connects the interior to the exterior of the hopper. Surrounding the chemical inlet pipe are a plurality of nozzles for introduction of solvation liquid into the hopper. The nozzles are disposed such that the solvation liquid washes the interior surface of the hopper to prevent plugging by hydrates (solvates) which may be formed. The outlet end of the hopper is connected to a suction opening of the liquid driven eductor.
Liquid driven eductors do not require large volumes of air or steam and can be used to transfer dry chemicals from a container, such as a railroad car, forming a solution or slurry of the chemical in the liquid carrier medium. In operation, liquid flowing through the eductor creates a suction and draws dry chemical out of the storage container and into the hopper. In the hopper, solvation liquid is supplied through the nozzles to wet the dry chemical and to wash the surfaces of the hopper, pushing the wetted material toward the outlet end of the hopper. At the outlet end of the hopper, the wetted material is sucked out into the eductor where it is combined with the flow of eductor liquid. The material leaving the eductor is recovered and sent to storage or directly for processing. The process and apparatus are particularly useful for handling soda ash, or calcium chloride.
Blockages in the hydrator of U.S. Pat. No. 4,884,925 have occurred with slurry storage systems at expected unloading rates. However, units discharging to solution storage systems have exhibited none of these difficulties on a long term basis. Frequent plugging of the hydrator has been attributed to fineness of the soda ash, lumps in the soda ash, or improper hydrator operation. To clear the blockages, the flow of soda ash has been decreased or derated, or additional labor has been provided to routinely unplug the hydrator. Internal blockages may have been further aggravated by excessive temperatures that promote flashing of the solvation liquid with resulting additional blockages, all of which can render the hydrator unproductive, and require the shutdown of the system for a long period of time.
U.S. Pat. No. 5,071,289 relates to a particulate delivery system having a closed storage hopper for the material, an eductor, and a gas inlet and feed valve. To remove blockages, the apparatus includes a purge mode where the hopper and feed valves are closed, a stir valve is activated, and pressurized gas is fed into the hopper in an upward motion.